Seasonal rhythms: the role of thyrotropin and thyroid hormones.

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Seasonal rhythms: the role of thyrotropin and thyroid hormones.

Thyroid. 2017 Sep 06;:

Authors: Nakayama T, Yoshimura T

Abstract
Seasonal changes in various physiological events have been reported in humans including metabolism, immune function, and mood. However, the molecular and endocrine basis of the seasonal changes remain unclear. Animals that breed seasonally such as, the Japanese quail and Siberian hamster have sophisticated seasonal mechanisms and provide excellent opportunities to understand the underlying processes. Functional genomic analysis of the quail uncovered the photoperiodic signal transduction pathway, which regulates avian seasonal reproduction: Long day stimulus induces secretion of the thyroid-stimulating hormone (TSH) from the pars tuberalis (PT) of the anterior pituitary gland. The PT-derived TSH locally activates the thyroid hormones within the hypothalamus, which in turn induces the gonadotropin-releasing hormone (GnRH) and consequently gonadotropin secretion. Studies using TSH receptor-null mice confirmed the involvement of the PT-derived TSH in mammalian seasonal reproduction. The pars distalis (PD) of the anterior pituitary gland is the major source of circulating TSH. Although the PD and PT are closely localized, tissue-specific glycosylation of the circulating TSH adds diversity to its function, to avoid crosstalk.

PMID: 28874095 [PubMed - as supplied by publisher]

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